An optical fingerprint imaging system can implement fingerprint image capturing based on light reflection/refraction, and light sensing. Specifically, when a finger touches an active area of the optical fingerprint imaging system, light emitted from the fingerprint imaging system will reach the interface between the fingerprint imaging system and the finger, and be partially reflected at the interface. As light reflected at different regions of the interface, (e.g., where touched by ridge or valley of the finger) may have different intensities, features of a fingerprint corresponding to the finger can be represented based on the light intensity variations. In some solutions, the reflected light may be received by a sensor, then converted into electronic signals. As such, a fingerprint image can be obtained based on processing the electronic signals.
Referring to FIG. 1, an existing optical fingerprint imaging system 100 is illustrated. The optical fingerprint imaging system 100 includes a backlight source 101, an optical array sensor 102, and a cover plate 103. When a finger 20 touches the cover plate 103, light emitted from the backlight source 101 penetrates through the optical array sensor 102 and the cover plate 103, and reaches an interface between the finger 20 and the cover plate 103. Light reflection and refraction occur at the interface. The reflected light penetrates through the cover plate 103 and reaches the optical array sensor 102. The optical array sensor 102, including an array of pixels (e.g., photodiode or transistor), implements photo-electronic conversion to the received reflected light. Thus, electronic signals proportional to the intensity of the reflected light are obtained, based on which a fingerprint image of the finger 20 can be generated.
However, in existing optical fingerprint imaging systems, light reflected at a specific point of the interface may transmit in various directions, thus it may not only reach the corresponding pixel disposed right below the specific point of the interface, but also irradiate to the other neighboring pixels. As a result, the final obtained fingerprint image may be blurred.
Therefore, an optical fingerprint imaging system, which is able to obtain a fingerprint image in high contrast, is required.